How to Make Magnetic Slime

Did you know that it’s possible to make slime that is magnetic? Magnetic slime has iron in it and is attracted to a strong magnet. It is super stretchy and so much fun. When you hold a magnet near the slime, it oozes toward it, and the slime will “swallow” up a magnet if you let it go! SO COOL.

Magnetic slime is easy to make with our 3 ingredient recipe!

This post was originally written in March 2014 and updated in April 2019. Our updated recipe is easier to follow and is much less messy! Slime has a bad reputation for being messy, and you may be afraid of a “slime fail.” I can assure you, however, that this project will be fun and successful! I do recommend reading the instructions carefully, and you’ll want to try out this project first before doing it with a group.

Magnetic slime is really fun to play with on its own. It stretches and squishes. If you hold it up, it oozes down to the floor in a long strand! Adding the element of magnet play makes it even more awesome. This is a great project to put on your to-do list for a rainy day, spring break, or summer! It would also make a great group activity for a science club or scouting group.

There’s just something about watching a liquid move without touching it… So fascinating!

You can get the slime to move faster if you let the magnet touch it. It’s also cool to feel the magnet stick to the slime.

We also had fun putting the magnet on top of the slime and watching the slime swallow it up!

Supplies Needed for Making Magnetic Slime

These links are Amazon affiliate links, meaning that if you purchase through the links, I will earn a small percentage of the sale at no extra cost to you.

A neodymium (rare earth) magnet – A regular magnet won’t be strong enough. Here’s a set on Amazon with two Neodymium Barr Magnets. We ordered ours awhile back, but our Amazon history says we used this link, although the magnets look slightly different.

How to Make Magnetic Slime:

Step 1: Pour 1/4 cup of white PVA glue into your mixing bowl. You may have to use the spoon to scrape all the glue out of the measuring cup.

Step 2: Add 2 Tablespoons of iron oxide powder. Stir well.

You’ll be expecting the mixture to look solid black, like my photo of the slime above. However, it will look more like Oreo cookie crumbs! Don’t worry – it will look solid black in a minute.

Step 3: Pour in 1/8 cup of liquid starch.

Step 4: Stir the glue and starch mixture really well to make sure that it’s all mixed. As soon as you begin to stir, the starch will react with the glue and the slime will start to form.

I ended up with a little bit too much starch. The way I could tell is that there was some unmixed starch in the bowl and on the slime after I had stirred it well. To fix this, I rinsed the slime for just a few seconds under cold water.

Step 5: Knead the slime with your hands.

This is how the slime looked after a quick rinse and a little bit of kneading. I find that it helps to wash my hands after kneading the slime and before playing with it. This helps to make the slime less sticky.

Troubleshooting:

If your slime is too sticky (glue-y), knead in a tiny bit more starch. If it’s too stringy, knead in a little more glue.

If your slime does not respond to your magnet, the problem is the strength of your magnet. We ordered some new cylinder neodymium magnets which did not turn out to be strong enough!

Here are a couple more important notes:

Neodymium magnets are extremely strong! Fingers can easily get pinched when trying to separate the magnets. Be sure to keep the magnets away from cell phones, computer, and other electronics. If you order the smaller disc magnets, make sure that no one puts them in their mouth – these would be very dangerous if swallowed. Overall, this is not a project for kids who still put things in their mouths.

Iron oxide powder is not good to breathe. This is why we mixed our iron in with the glue. I have seen some recipes on the internet that recommend kneading the iron oxide powder into the finished slime. We tried that approach, and besides being super messy, I think it’s much more likely to stir up the iron oxide dust.

If making magnetic slime seems like too much of a hassle, you can actually purchase magnetic silly putty – Crazy Aaron’s Thinking Putty which comes with a magnet and does the same thing. (Although judging by the reviews, I think the homemade slime responds better to the magnet!)

I think this is such a wonderful site!!! Being a mom of two boys, I happened upon this site when they’re crying in despair because they are so bored. We had made the liquid starch ourselves because I didn’t have any. Because we *really* wanted to make this amazing goo and didn’t have any ferrous powdered metals around (that I knew of), I decided it might be kind of cool to make our own. Go science! So for others who happen by this site – a good substitute for the ferrous oxide would be laser printer powder (if you have it handy). Otherwise, I highly recommend you order it online because making it yourself (especially with kids around) is either extremely dangerous or takes forever.

Please be aware that magnets of this strength can cause havoc and even death if swallowed. It would be best to leave them stacked and then wrap them with electrical or duct tape to avoid the temptation to play with them individually. Otherwise, a very interesting activity.

I also notice that the iron oxide powder on Amazon comes in red, as well. Is there any functional difference in the two?

Sorry to be nerdling on this issue. There is no major difference other than the compound structure. Each should work as well as the other. The difference in color is caused by the difference in oxidization, really. I think it’s also heated and the black may be a bit more prone to magnets. Don’t quote me on that. But both have Fe and it’s simply (again, I think) an extra oxygen molecule on one than the other (or was that less.)

This would be very poisonous, wouldn’t it? I remember reading somewhere about letting little kids play with iron shavings and magnets, that they can be poisoned by very small amounts. No doubt this is too disgusting to eat on purpose but what about little ones getting it in their mouths by accident?

I looked up the material safety data sheet for black iron oxide, and it is listed as non-toxic. The main risk is irritation from inhaling it, but with the way it is used in this activity, that should not be a major problem. Sensitive individuals could always wear a mask. The msds says to seek medical attention for ingesting large quantities. With proper supervision, I don’t know why anyone would ingest any quantity of this! It’s definitely not for kids who still put things in their mouths! I hope that answers your question. This is a science project, and proper precautions should be taken as such.

FE304 is not listed as non-toxic, but rather a hazardous substance that is regulated by OSHA. Every copy of an MSDS I have seen on FE304 (which is the chemical you link to in your recipe) recommends full PPE, including eye protection, gloves, and mask. I’m an environmental health scientist by training, and I would definitely be considered about potential risks in this experiment.

I’m a chemistry professor and I’ve done this experiment many times in K-12 classrooms, summer camps, etc. It is super fun and teaches about both polymers and magnets. My recipe uses 20 Mule Team Borax and water rather than Sta-Flo (its the sodium tetraborate in both that cross-links with the PVA in the glue to make slime). As far as the safety goes, many iron oxides such as this one are used in tattoo inks (Fe3O4 and FeO in black, and Fe2O3/rust in red). The biggest concern would be ingesting and breathing it in large quantities. I always spoon it out myself into the kids’ baggies full of glue which also curbs the mess. Once the powder is incorporated into the slime, it stays there. I’ve made it with my three year old and he plays with it all the time. One bag is nearly a year old and is still good, although I sometimes need to add a bit of water.

I’ve made it many times… I use a teaspoon of borax in a 1/2 cup of hot water. Sometimes the borax doesn’t dissolve completely, and it still works perfectly. I use 2 4 oz bottles of Elmer’s glue then 2 bottles full of hot water and mix that along with food coloring before I mix in the borax solution. Hope that helps!

Shelly– Christmas presents! Either premixed, and labeled with a set of magnets on the side, or a baggie of it along with a list of the other ingredients needed (since it is the hardest one to find!) It could be a frugal gift for little friends! 🙂

Her advice along with my own experience leads to the following advice:

Slime that is too sticky/gooey needs more starch. GEnerally just dipping hands in a little starch will help it to firm up AND keep it from sticking so badly to hands.

Slime that becomes stringy needs more glue (add in small amounts).

Slime lasts almost indefinitely when covered tightly or stored in a baggie. “Fresh” slime will get a little gooey when covered tightly but will soon dry out with play/airtime. Slime that’s getting a little too dry can be revived by playing with it with hands dampened with a little water.

Yes, the girls love it just as much as the boys and fifth graders just as much as my firsties!

This is definitely not just for boys! The name of my site is Frugal Fun for Boys because I have four boys. As a mom of boys, I know that it’s harder to find crafts and activities that boys will go for, so this site is designed to be a resource for moms of boys. However, that doesn’t mean that girls wouldn’t enjoy many of these activities!

Iron oxide is easy to make with a piece of iron, some DC current and a container of water. Attach the iron to the positive wire and stick it in the water, add a tiny bit of salt for conductivity, put the negative opposite the positive in the water and turn on the power. I used to use a train transformer because it could vary the amount of current. Once the electric starts flowing you will see bubbles released from the iron, this is the oxidation happening, Wikipedia is your friend when doing stuff like this. Extra iron oxide can be mixed 50/50 with powdered aluminum to make a whole other science project, thermite, which is way fun but very very dangerous. When it burns, it burns at 5000 degrees. It can be used like the railroad companies use it to weld train tracks together, or it could be used to melt a hole through the engine block of a car, ya know whatever, very versatile

I am hoping to do this with the entire 5th grade at my son’s school. (approx 75 kids) Did you use the 10 magnets per child? Did your foursome split the magnet? How would you suggest I do it for such a large group? I like the baggie idea the chemist previously suggested.

We used all 10 magnets as one unit – the kids just passed it around. For 75 kids, especially since they are 5th grade and won’t be putting the magnets in their mouths, I think you could probably do a chunk of 3 magnets stuck together. Maybe plan to share the magnets among groups of 4 students? You definitely don’t need a magnet for each child. The slime is fun enough on its own while they wait for a turn with the magnet. But if you do single magnets, they are harder to hold onto and would be easier to lose. That’s why I’m thinking chunks of 3 stuck together. Just my opinion – not sure if that helps or not!

Actually I tried this with my granddaughter and it turned a grayish color so we added a small amount of black gel food coloring and after a lot of kneading we achieved the black we were looking for! Once you have worked the putty well, color did not stain her hands! Really happy with the slime!

I’m excited! We are making this today with our little homeschooled group. I’ve done slime with the borax before, but the starch was so cheap at Walmart (near the fabric softener) that I figured we could do it both ways if one doesn’t work well.
Thank you for posting this. If we have any suggestions afterward, we’ll let you know. (I like the Baggie idea).
Magnets are so strong…once your able to remove one, it’s got to be kept far from the others. I let the magnets get too close and they snapped together so fast that the corner broke. Oops. Be safe.

OK, what did I do wrong? Made this today and it was a stringy mess! We mixed the iron oxide really well with the starch before we added the glue. Used Elmers White Glue, then patted it a lot with paper towels. Still kept getting black on our hands. We were really disappointed that it didn’t work.

You were so close! If you have enough materials, try it again! If it’s stringy and a sticky mess, add a little more starch and keep mixing. An easy way to do this is to dip the whole blob in some starch, then keep kneading it. Try washing your hands well, then squeezing some more. Once you have enough starch and it’s well mixed it will stop being stringy. I hope this helps – let me know!

I would think that iron filings would not work as well as iron powder due to the size of particles. The filings wouldn’t mix in with the polymer as well and may end up with jagged/sharp part protruding.

People looking for something to do with excess iron powder…try to make your own hot hands hand warmers. Iron powder, water, and salt are the 3 main ingredients in most hand warmers. The reaction of iron and oxygen creating rust is exothermic and will produce heat. Simply put the iron in a cup or bag, add a pinch of salt and an eyedropper or 2 of water. It should heat up fairly quickly but not so much that it will burn anything.

Still, as mentioned earlier the fine powder is harmful if inhaled so use caution with children!

Sorry I know this post is really old but I was wondering if it would it be possible to use the hot hands instead of buying the iron oxide? Or would the other ingredients in the hot hands affect it in some way? I want to make some with some elementary students.

TEACHERS/GROUP LEADERS: Since I need at least 10- 12 magnets for groups of students to use, I need a better price on magnets. I checked the prices at Harbor Freight since I have one just down the road. It carries 10 much smaller rare earth magnets for $2.99. I believe that by doubling them, the magnets will be strong enough at a fraction of the price. It seems worth checking out.

Comparison: Amazon’s are 1 1/2″ diameter 1/4″ thick and are Grade N45 – 32 lb Per Magnet. Harbor Freight’s are 5/6 diameter and 1/8″ thick, but did not have any grade or pull shown on the website. I’m hoping for the best when I go in.

I did order the Black Iron Oxide from this site – thank you so much for the recipe and the link for the oxide. I wouldn’t have thought of Amazon for that!

It only takes a few minutes to mix up, but I think that the time needed would also depend on the age of the students, how many students you have, how many adults are helping, and what your classroom set-up is like. Lots of factors!

Yes, I was able to get black sands to work; I tripled the amount called for here. The bonus is they don’t stain. I used a magnet and a plastic dish to make sure the black sands were mostly magnetic, and not just black minerals. I collected the black sands from the beach at Fort Funston in San Francisco.

We tried the experiment three different times, mixing in different types of bowls and did not have the results we expected. I can’t seem to get the consistency to move from liquid to slime. On the second try, I dumped the mixture from the glass bowl to a plate with paper towel, to sop up some extra liquid. No dice. Just less “slime” because it soaked into the paper towel and a GIANT mess. 1/4 cup starch, 2TBSP iron oxide powder, 1/4 cup glue. What are we doing wrong? Mixing with bare hands or gloved hands only results in sooo much of the slime sticking to our hands that there is just less overall slime. We have enough iron powder and starch to try again. And glue is cheap. 😉 I’d like to give it one more go – but with success. Thanks!

Okay, here is what I would recommend. If the slime-y mess is so sticky that it’s sticking to your fingers, add more starch a little at a time. Knead in the starch with your hands. When I have “fixed” slime this way, it immediately stops sticking to my hands. If it feels too wet after mixing in more starch, try running the blob under running water for a few seconds, then pat dry with a paper towel. My good friend Asia at Fun at Home with Kids has written an excellent post on how to fix failed slime with pictures! Check out this link: http://www.funathomewithkids.com/2014/06/how-to-fix-slime-that-didnt-work-out.html

Yes, Amazon does not seem to have the exact set that I ordered anymore! Boo! The ones I linked to did not say neodymium in the description but they came up when I searched neodymium magnets and seemed to be strong, but I am not 100% sure. So I went ahead and updated the links in the post to show two different options that cost a little more, but I am confident that they are truly neodymium magnets and should work for this project!

Made this last night with iron filings. It worked just fine, they did not poke. The slime turned out grey with black speckles BUT it did not turn your hand black (plus side). The only downside it that the iron filings will rust. The iron will rust within 12 hours. But the slime will still be magnetic. We made this for a science fair so the fact that it rusted added just a little more for them to talk about.

My name is Tina I’m a grandmother of 3 I would like to be able to make this experiment at home with my three grandchildren you said your recommended ordering them online at Amazon is there a kit and if so what is it called could you please tell me thank you

I have made this with my own kids and at school. The starch came from our local Dillon’s (a Kroger brand) and the glue is easy to find anywhere. I got the iron oxide https://www.amazon.com/gp/product/B008LEOMJC/ref=oh_aui_detailpage_o09_s00?ie=UTF8&psc=1 and magnets from Amazon. The magnets are super strong and are hard to get apart, but when you do, they can give a painful pinch and small, sharp pieces will sometimes break off when they snap together (they look like white ceramic under the silver coating when they chip). I just ordered a neodymium bar magnet to prevent this issue.

I wanted to provide some helpful tips for anyone interested in a recent update as my daughter and I made this today. She makes her slime by adding the liquid starch to the glue in small increments until it reaches the consistency she desires. We tried making the magnetic slime the way the instructions indicated and weren’t pleased with the outcome. We tried it again adding the black iron oxide to the glue first instead of the liquid starch. After we completely mixed the iron oxide and glue, we added the liquid starch to the mixture until it reached the desired consistency. It turned out much better by adding the iron oxide to the glue first, and we ended up using a little less than 1/4 cup liquid starch. This method didn’t require drying the slime with paper towels either. We did use gloves to mix it until it was completely incorporated. I had no difficulty finding everything but the iron oxide at our local stores. The starch and glue were available at our local Walmart, but I ordered larger containers of the glue and liquid starch online at Walmart.com to be shipped to the store for free as my daughter makes large quantities or various slimes. I purchased the neodymium disc “Super Magnets” from Home Depot. They had a good selection of various sizes, too. I ordered the black synthetic iron oxide on Amazon. We wrapped one set of 3 disc magnets in plastic wrap to keep them clean while we played with the slime. (I believe someone else suggested wrapping them in electrical tape.) We also put another set of 3 magnets in a ziplock bag. My daughter preferred playing with the magnets that were in a ziplock bag as they were easier to extract from the slime. Perhaps someone will find this information helpful.

Thank you so much, Sarah, for posting this information, providing the measurements for ingredients, and pictures to go along with clear instructions! We greatly appreciate you!

This is such a great project! I’m a youth services librarian and am going to do this project with 40 tweens (!!!), but I’m looking for affordable rare earth magnets that are large enough for them to hold. It looks like you kept them in stacks of 10 – how large were your magnets? And while I usually default to Amazon, it doesn’t look like they have large quantities in my price range (so I’ve been looking at Walmart and Lowe’s also) – any suggestions for this? Thanks for your great post!

This looks like so much fun! I can’t wait to be able to do this with my friends and family! My science teacher even agreed to doing this for a class period! Yay! But I can’t wait. The only thing is I don’t know where the find the iron oxide stuff. I couldn’t find it on amazon and I don’t know anywhere else to find it. Also I wish there was a way to make colored magnetic slime.

We mixed the iron oxide with the glue first and then mixed in the liquid startch. The outcome is not magnetic. Is it because of the order we mixed? Trying to figure out what we did wrong because we are doing a science Fair project that is due Thursday!! Please help!!!

That’s not a fail! Next time, I would definitely try salvaging what you can. Then try kneading a little more starch into the slime. Sometimes I dip the slime in a little starch and then squish it around. That fixes the stickiness!

I’m making this slime with my daughter for her Science fair. Ours is getting really tough, chunky, not slimy and not moving.
Are we over mixing during the adding glue stage? Approx how much liquid will be at the bottom when we pull it out?

This is fantastic. The only thing I did different is put the iron oxide in the glue instead of the starch. All of the iron stayed in the glue. I also tried mixing the glue with the iron oxide, then adding Borax Water (1 tsp borax mixed in a 1/2 cup water until mostly dissolved). I added small amounts of the borax water until the slime was the consistency i wanted.

We love this activity and want to use it at a training workshop. We made the slime and put it in a ziplock bag. The magnets did not react at all. Is this because of the ziplock? Is it hard to get the slime off the magnet?

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Did This last year in Science night and it worked fine. The magnets did not work like in the picture. Tried it again this year, and the slime would just attract to the magnets. What could I be doing wrong?

[…] Magnetic Slime: This is one of those things that technically, probably isn’t related to Star Wars, but since the new movie isn’t out, I’m sure I can find a way to make it fit. And it’s really, really, cool and my younger teens love playing with it. […]

[…] or iron oxide (Fe3O4), Elmer’s glue, Starch (liquid), and some bowls to mix it up in. Here are the instructions to make it, the page calls for other magnets but those aren’t necessary because the iron […]

[…] or iron oxide (Fe3O4), Elmer’s glue, Starch (liquid), and some bowls to mix it up in. Here are the instructions to make it, the page calls for other magnets but those aren’t necessary because the iron […]

[…] Magnetic Slime is awesome because you get to mess around with magnets and you get to make slime! This can just be something you have around, leave it in a container on the coffee table and when guests come over while you’re cooking or while you are watching a movie they have an activity that allows them to focus on watching or talking but lets them fidget around! Also it just looks like Venom a little bit and that’s such a happy thought. […]